report of 2016 findings

Crab Team in Washington State report of 2016 findings

Prepared by Emily Grason Team Program Coordinator Washington Sea Grant

November 2017 November 2017 Report Prepared by Emily Grason Crab Team Program Coordinator [email protected]

CONTENTS Infographic...... 1 Summary...... 2 1. Monitoring Network...... 3 2. Baited Trapping ...... 4 3. Molt Surveys...... 14 4. Habitat Transect Surveys...... 17 Closing Thoughts...... 20

Note: Data presented here are in summary form only. Please contact Crab Team directly before reuse or for access to the raw data for additional analysis.

COVER PHOTO CREDIT: EMILY GRASON 2 INFOGRAPHIC

report of 2016 findings

1 Summary

rab Team is a project of Washington Sea Grant in which volunteers conduct early-detection monitoring for European green crab () across CWashington’s inland shorelines. Launched in 2015, Crab Team expanded to monitor 26 sites from Nisqually Reach to Bellingham, and as far west as the Dungeness River in 2016. Volunteers conduct monthly surveys that include baited trapping, molt searches and a habitat transect survey. While the primary goal of the project and monitoring protocols is to detect green crab at the earliest possible stage of invasion, volunteers collect data on all observed during trapping and molt surveys. These data on native , fishes and habitat features are the beginning of a longitudinal regional dataset on pocket estuary and salt marsh habitats in Washington’s Salish Sea. Information from these sites will provide valuable insight into the health and dynamics of these understudied habitats and the impacts that green crab could have on them.

Here, we present a summary of Crab Team’s monitoring data from 2016 intended to highlight the contributions of the volunteers and the value of the dataset. The most notable finding in 2016 was the capture of a European green crab by Crab Team volunteers in Westcott Bay, on San Juan Island. Fortunately, the single green crab was only one of more than 57,000 organisms observed during surveys. These data offer a broad and rich opportunity for exploring local shorelines from ecological, conservation and stewardship perspectives.

What follows are snapshots of Crab Team work during 2016, with brief interpretation of what the observed patterns might mean. As monitoring continues, and multiple years of data are assembled, we will be able to gain more insight into seasonal patterns and temporal trends. As Crab Team is a true collaboration with volunteers, we invite discussion. For more information on Crab Team, including survey protocols, visit the website: wsg.washington.edu/crabteam or email [email protected].

2 1. Monitoring Network

uget Sound, the Strait of Juan de Fuca and the a needle in a haystack. Monitoring sites are selected San Juan Islands together constitute Washington’s based on suitability for green crab survival, availability PSalish Sea, which has nearly 2,500 miles of of monitors and proximity to other sites. Crab Team shoreline. It’s no exaggeration to say that looking for monitored 26 sites in 2016, and identified 183 as a single, or even a few, green crab is like looking for potentially suitable habitat for green crab (Figure 1).

report of 2016 findings

Sooke Basin, BC Green crab detected in 2012

Suitable Habitat Medium and High habitat suitability Medium High Crab Team monitoring sites (26)

Figure 1. Map of suitable habitat for European green crab, and Crab Team monitoring sites during 2016.

3 2. Baited Trapping

ach month, monitors set six baited traps— three each of cylindrical minnow and square EFukui styles—for an overnight soak. All native organisms are identified and counted before being released, so Crab Team can compare the ecological Highlights communities of organisms that live at sites and how they change over the season. • A total of 828 traps were set in 2016, totaling 18,696 soak hours (779 days). This section provides some insight into what Crab Team captured in traps, as well as patterns of • Of 44,216 organisms, and 25 species, abundance and diversity across the 26 monitoring only a single European green crab was sites during 2016. We summarize the total catch by captured. species for the year in different ways. A species might be abundant, meaning large numbers are trapped • Trap catches were vastly dominated by (Table 1) , or it might be common (Table 2), meaning native hairy shore crab ( it is found at many of the sites, or it might be both oregonensis), which were present at abundant and common. Exploring species abundance every single site. and commonness across all sites (Table 3) enables us to get at questions of diversity and ecosystem • Staghorn sculpin was the distant productivity. second-most abundant organism, but still found at nearly every site.

• Both richness (number of species) and diversity are negatively correlated with total number of organisms trapped. That is, the more individual captured, the greater the dominance by hairy shore crab, and the fewer different types of captured.

• The number of organisms caught that were not hairy shore crabs was fairly consistent across all sites. Totaled over the season, each site caught slightly fewer than 200 critters other than hairy PHOTO CREDIT: CRAIG STAUDE shore crab during 2016—regardless

The first European green crab detected along of how many hairy shore crab were Washington’s inland shorelines was captured by Crab caught. Team volunteers at Westcott Bay in August 2016, and appears along with the other fish captured in the same trap.

4 Table 1. Trap Catch Totals by Species. Total number of each Table 2. Commonness of Animals Trapped. Number of sites species captured in trapping surveys across all sites and at which each species captured in trapping surveys was found months during the 2016 monitoring season. during 2016 monitoring season.

Species 2016 Common Name # Trapped Taxon Species Common Name # Sites Where Type Captured Hairy shore crab 41,006 (of possible 26)

Leptocottus armatus Staghorn sculpin 1,505 Crab Hemigrapsus oregonensis Hairy shore crab 26

Cancer () gracilis Graceful crab 270 Fish Leptocottus armatus Staghorn sculpin 25

Nassarius fraterculus Japanese nassa 231 Crab Hemigrapsus nudus 17

Hemigrapsus nudus Purple shore crab 228 Fish reportGasterosteus aculeatus ofThree-spined 2016 stickleback 13 findings

Pagurus granosimanus Grainy-handed hermit crab 188 Crab Pagurus hirsutiusculus Hairy hermit crab 12

Gasterosteus aculeatus Three-spined stickleback 172 Fish Cymatogaster aggregata Shiner perch 12

Batillaria attramentaria Asian mud snail 167 Crab Pagurus granosimanus Grainy-handed hermit crab 8

Cancer (Metacarcinus) magister 110 Crab Cancer (Metacarcinus) gracilis Graceful crab 6

Pagurus hirsutiusculus Hairy hermit crab 101 Snail Batillaria attramentaria Asian mud snail 6

Cottus asper Prickly sculpin 64 Crab Cancer (Metacarcinus) magister Dungeness crab 5

Cymatogaster aggregata Shiner perch 42 Fish Pholidae and Stichaeidae spp. Eel-like fishes (e.g. gunnels) 3

Haminoea sp. Bubble shell 34 Crab Red rock crab 2

Amphissa columbiana Wrinkled dove snail 27 Crab Multiple in Majidae Spider crabs 2

Cancer productus Red rock crab 22 Crab Telmessus cheiragonus Hairy helmet crab 2

Nassarius mendica Western lean nassa 14 Snail Haminoea sp. Bubble shell 2

Pholidae and Stichaeidae spp. Eel-like fishes (gunnels, pricklebacks, etc) 10 Fish Oligocottus maculosus Tidepool sculpin 1

Pandalidae and Hyppolytidae spp. Broken back shrimp 6 Fish Syngnathus leptorhynchus Bay pipefish 2

Multiple in Majidae Spider crabs 5 Crab Carcinus maenas European green crab 1

Oligocottus maculosus Tidepool sculpin 4 Crab Lophopanopeus bellus Black clawed crab 1

Telmessus cheiragonus Helmet crab 4 Shrimp Pandalidae & Hyppolytidae spp. Broken back shrimp 1

Syngnathus leptorhynchus Bay pipefish 3 Snail Amphissa columbiana Wrinkled dove snail 1

Carcinus maenas European green crab 1 Snail Nassarius fraterculus Japanese nassa 1

Lophopanopeus bellus Black clawed crab 1 Snail Nassarius mendica Western lean nassa 1

Porichthys notatus Plainfin midshipman 1 Fish Cottus asper Prickly sculpin 1

Total 44,216 Fish Porichthys notatus Painfin midshipman 1

Fish Platichthys stellatus Starry flounder 1

5 771 962 426 202 948 422 317 464 652 433 332

1,275 3,221 4,163 2,649 2,706 1,162 1,047 5,277 1,895 3,092 4,401 2,163 2,368 1,092 1,776

TOTAL 44,216 Months Sampled Months

6 6 2 6 6 6 6 6 6 5 6 6 6 3 6 6 6 6 6 5 6 6 2 4 6 4 Nassarius mendica Nassarius

14 14 Nassarius fraterculus Nassarius

231 231 Amphissa columbiana Amphissa

27 27 Haminoea spp. Haminoea 19 15 34

Gastropods Batillaria attramentaria Batillaria 8 3 3

29 21

103 167 Porichthys notatus Porichthys

1 1 Sygnathus leptorhynchus Sygnathus

1 3 2 Oligocottus maculosus Oligocottus 4 4

Eel-like fishes Eel-like

1 1 8

10 Cottus asper Cottus

64 64 Fishes

Cymatogaster aggregata Cymatogaster 1 7 2 1 6 2 1 1 2 2 3

42 14 Gasterosteus aculeatus Gasterosteus 1 2 1 1 4 2 2 2 5 81 21 50 172

7 4 3 8 7 4 7 5 Leptocottus armatus Leptocottus 13 56 31 99 76 45 68 74 23 22 14 55 39 78 16 414 160 177

1,505 Broken back shrimp back Broken

6 6

Pagurus granosimanus Pagurus 4 9 5 3

18 14 48 Pagurus hirsutiusculus Pagurus 2 4 1 1 4 3 3 2 1

26 32

109 188 101 Carcinus maenas Carcinus

1 1

bellus Lophopanopeus

1 1 Telmessus cheiragonus Telmessus

1 3 4

Majidae - - Majidae Spider crabs Spider

1 4 5 Cancer productus Cancer 2

20 22

Crustaceans Cancer (Metacarcinus) magister (Metacarcinus) Cancer 1 1 9 1

98 Cancer (Metacarcinus) gracilis (Metacarcinus) Cancer 6 5 1 92

166 Hemigrapsus nudus Hemigrapsus 1 1 3 3 4 2 6 6 2 1

25 13 18 78 36 18 11

228 270 110 Hemigrapsus oregonensis Hemigrapsus 16 93 729 337 111 696 274 971 385 522 934 122 416 1,069 1,139 5,244 1,716 1,884 3,082 3,185 4,103 2,605 4,360 2,059 2,327 2,627 41,006

Region San Juan Island Bay Island Juan Bellingham Island Juan San Juan San JDF Bay San JDF of Fidalgo of Strait Basin Strait Basin Whidbey Basin Whidbey Basin Whidbey Basin Whidbey Inlet Whidbey Inlet Admiralty Inlet Admiralty Canal Admiralty Canal Hood Canal Hood Canal Hood Sound Hood Sound Central Sound Central Sound Central Sound Central Sound Central Sound Central South

2016 Trap Catch by Site. Total number of each species captured in trapping surveys organism type and individual site during monitoring season. Site Name . Musqueti Post Point Bay Post Lagoon Westcott Bay Third Spit Mud Bay Crandall River Discovery Lagoon Dungeness Cove Kiket Lagoon Penn Spit Race Bay Iverson Lagoon Elger Lagoon Kala Point Deer Point Lagoon Zelatched Lagoon Duckabush Nick’s Wats Creek Kag Carpenter Lagoon Doe Harbor Best Blakely Lagoon Heyer Cove Rabb’s Butterball TOTAL 74 362 533 536 330 341 198 214 323 311 508 516 552 204 306 590 161 138 128 177 173 133 553 579 581 250 Site

Table 3

6 How “Diverse” Is Diverse? 771 962 426 202 948 422 317 464 652 433 332 Another way to look at ecological communities of 1,275 3,221 4,163 2,649 2,706 1,162 1,047 5,277 1,895 3,092 4,401 2,163 2,368 1,092 1,776 44,216 Patterns of Abundance and Diversity pocket estuaries is how widespread each species 6 6 2 6 6 6 6 6 6 5 6 6 6 3 6 6 6 6 6 5 6 6 2 4 6 4 is across all of the sites sampled. Figure 3 is 14 14 A rank abundance curve (RAC) orders each species a histogram, where each species is listed by the found in traps by their proportion of the total (Figure 231 231 number of sites at which it was trapped. So, for 2). The steepness of the line provides insight into how 27 27 example, the furthest left grey bar indicates that evenly organisms are divided among species. If the 10 of the species captured were found only at one 19 15 34 line is horizontal, all species are equally abundant. site—they are rare species, uncommon in these 8 3 3

29 21 The RAC for trap contents of 2016 is extremely 103 167 habitats. On the other end, two species were steep because hairy shore crab made up 93% of all 1 1 found at nearly all of the sites: staghorn sculpin organisms captured. This indicates that, in general, 1 3 2 was found at 25 sites, and hairy shore crab was found the community of mobile animals in pocket at all 26 sites. This shows us that most species we

4 4 estuaries that is sampled in baited traps is not a foundreport are uncommon in pocket of estuaries, 2016 limited findings

1 1 8 very “even” one. Keep in mind, however, that not all 10 to one or two sites. A handful, such as purple shore organisms that live in these habitats will come to a crab, stickleback and hermit crabs, are intermediate. 64 64 baited trap. Only a very few species are common in traps. 1 7 2 1 6 2 1 1 2 2 3 42 14 1 2 1 1 4 2 2 2 5 81 21 50 172 � 7 4 3 8 7 4 7 5 13 56 31 99 76 45 68 74 23 22 14 55 39 78 16 414 160 177 1,505 0.80.8 6 6 4 9 5 3 18 14 48 2 4 1 1 4 3 3 2 1 0.60.6 26 32 109 188 101 1 1

0.40.4 1 1 1 3 4 Proportional Abundance 0.20.2 1 4 5 Proportional abundance 2 20 22 � � � � � � � � � � � � � � � � � � � � � � � �

1 1 9 1 0.00.0 98

5 1010 15 20 25 6 5 1 92 166 SpeciesSpecies Rank Rank 1 1 3 3 4 2 6 6 2 1 25 13 18 78 36 18 11 228 270 110 16 93

729 337 111 696 274 971 385 522 934 122 416 Figure 2. This rank abundance curve (RAC) puts each species Figure 3. Species commonness histogram showing how many 1,069 1,139 5,244 1,716 1,884 3,082 3,185 4,103 2,605 4,360 2,059 2,327 2,627 41,006 captured across the entire network in order from most to species were found at one or more sites. Each bar is the total least abundant and shows what proportion of the total of number of species that was found at the number of sites in- 44,216 animals captured in 2016 each made up. dicated by the horizontal axis. Rare species, those found only at a single site or a few sites, are on the right side of the plot,

San Juan Island Bay Island Juan Bellingham Island Juan San Juan San JDF Bay San JDF of Fidalgo of Strait Basin Strait Basin Whidbey Basin Whidbey Basin Whidbey Basin Whidbey Inlet Whidbey Inlet Admiralty Inlet Admiralty Canal Admiralty Canal Hood Canal Hood Canal Hood Sound Hood Sound Central Sound Central Sound Central Sound Central Sound Central Sound Central South and common species, those found at many sites, appear on

the right side of the plot.

Musqueti Post Point Bay Post Lagoon Westcott Bay Third Spit Mud Bay Crandall River Discovery Lagoon Dungeness Cove Kiket Lagoon Penn Spit Race Bay Iverson Lagoon Elger Lagoon Kala Point Deer Point Lagoon Zelatched Lagoon Duckabush Nick’s Wats Creek Kag Carpenter Lagoon Doe Harbor Best Blakely Lagoon Heyer Cove Rabb’s Butterball TOTAL 74

362 533 536 330 341 198 214 323 311 508 516 552 204 306 590 161 138 128 177 173 133 553 579 581 250 * Technically, because some of our observations group multiple species together (e.g., spider crabs, brokenback shrimp), the appropriate term

is “taxa” (or taxon for singular), which means groups of organisms of a type, rather than species.

7 Does Diversity and Abundance Change Note that the measure of abundance is the average Across the Salish Sea? number of organisms trapped per month, which allows us to adjust for the fact that some sites weren’t We found large differences in the number of individual sampled for the full six-month period. We made this animals and the number of species (or “taxa”*) adjustment because we would expect if you sample observed across all our sites. Some sites had only a more times, you’re likely to capture not only more handful of organisms in their traps each month, while organisms, but also more types of organisms, just others had thousands. Figure 4 gives some insight into because you sampled more, and not necessarily the scale of that variation. The marker for each site is because there are more types of organisms at that coded by size, where larger markers indicate a greater spot. Sites characterized by greater diversity were total number of animals found in traps during 2016, scattered across the region, with the most diverse and by color, where a darker marker indicates a greater sites being the northernmost (Post Point Lagoon number of taxa found at that site in traps during 2016. in Fairhaven) and one nearly southernmost (Rabb’s Lagoon, Vashon Island). Even sites that were close to each other seemed to be very dissimilar in abundance and diversity of critters.

This suggests that local factors that apply specifically to each site, such as temperature, or salinity, or tidal regime, could be more important than regional factors in influencing these two characteristics of ecological communities.

PHOTO CREDIT: P. SEAN MCDONALD

Figure 4. Map of total abundance and species richness Two European green crabs captured at Padilla Bay (number of taxa) of animals captured in traps across 26 Crab during 2016 rapid response trapping. Crab Team Team monitoring sites during 2016. Larger circles mark sites launched monitoring sites in Padilla Bay in 2017 in with more total animals trapped, and darker circles indicate response to these detections. that more taxa were found at that site.

8 Who and How Many? simultaneously closest to all the points or data. The Does Abundance Influence Diversity? number in the top right corner of the plot indicates the distance from the data to the line, or how well the When looking at the map (Figure 4), we noticed that estimated relationship (line) predicts the data we larger circles seemed generally lighter in color (i.e., actually observe (dots). This value can range from 0–1, sites that had a great abundance of organisms had and a higher value means the data are close to the fewer taxa). To explore whether this was just a trick of line, and the equation for the line has more accurate the eye, or a true pattern, we took the sites out of geo- predictive power. A lower value doesn’t necessarily graphic space and plotted them on XY axes. On the plot mean the relationship doesn’t exist, however. In in Figure 5, the color of the markers from the map ecology, such scatter often means that factors that denoting the total number of taxa observed at each aren’t measured in the equation for the line also site during 2016 trapping has been translated to the influence the outcome (taxa richness). So, if one site vertical axis, and the abundance of organisms—again is belowreport the line—fewer species of than expected2016 based findings as the average number per month—is plotted on the on the abundance—perhaps it is because that site is horizontal axis. Thus, the total for each site is a dot on heavily impacted by humans or experiences extremely this plot. To find a particular site, useTable 3. high temperatures. Interpreting relationships like this is at the heart of ecology, and it often gives starting points You’ll see there is a fair amount of scatter but, generally, for future questions. the sites with the most critters in their traps also had very few taxa, while the sites with the most The fit for the relationship between the number of taxa trapped fewer critters. The line on the plot taxa (richness) and the average number of individuals draws the ‘best-fit’ relationship between the number trapped per month, or the r2, is 0.35. This sounds low, of taxa and the number of critters*—he line that is but actually isn’t bad for an ecological relationship, Total site taxon richness

Figure 5. Relationship of taxa richness (left) and Diversity (H’, right) with average organism abundance per month in 2016 trapping surveys. Each point indicates a separate site. The lines plotted show the best fit of the data to a relationship with the natural log of organism abundance.

* If it looks like the line curves slightly, you have a good eye! The relationship was modeled not as a straight line, but using the natural log of abundance, which varies on an order of magnitude larger scale than taxon richness.

9 which is influenced by a lot of different contexts 5,000 simultaneously, and thus data often have a lot of spread. 4,000 The plot in Figure 5 has the same horizontal axis— abundance—but measures a different characteristic 3,000 of the community: true Diversity (with a capital D). We often think of diversity (in common usage), as being 2,000 simply the number of species (or taxa). That measure is usually called richness by ecologists and it is only 1,000 one way diversity can be measured. The evenness Total number of all organisms Total

(relative abundance) with which each of the species is 0 represented also matters. Intuitively, we think that a 0 1,000 2,000 3,000 4,000 5,000 cornfield is less diverse than a mixed forest because it Number of hairy shore crab is dominated by a single species; however, there may be just as many or more species present in the corn- Figure 6. Relationship of the total number of all organisms field if you count the “weeds.” The measure of in traps with the total number of hairy shore crab across all Diversity used here is the Shannon Index (denoted as sites in Crab Team monitoring network during 2016. Line is estimated line of best fit. H’), which includes both richness and evenness in the calculation. Increased richness and evenness will increase the Shannon Index for a site. This plot shows the same 26 sites by the same abundances on the go through the point (0, 0), but hits the vertical axis horizontal axis, but with a new measure of “diversity” on slightly above the horizontal axis. This means that even the vertical axis. when there aren’t any hairy shore crab at a site (which in this case is only a prediction because every single Given the fact that hairy shore crab comprise 93% site had at least one hairy shore crab in 2016), there of trap catch, it’s no surprise that there is an even are at least a few other organisms; to be precise, that’s stronger negative relationship (steeper line) of H’ with estimated to be 193 other organisms. abundance. In large part, this is because the sites that have the highest trap catches have the most hairy Lower evenness at sites with high abundance of critters shore crab, and therefore the lowest evenness. Want explains why there is a steeper decline in Diversity (H’) to see the data? with abundance, but it doesn’t explain why taxa richness apparently declines with abundance: Why would In Figure 6, we’ve shown the total number of all more individual animals mean fewer types of organisms at a site (no longer the average per month, animal? Shouldn’t it be the opposite? However, a but the total for all of 2016), which is now on the different face on the same question might be: why vertical axis, and the total number of hairy shore crab would more hairy shore crab mean fewer types of only on the horizontal axis. Each point still represents animal, because let’s face it, when we have more a single site. In this case, the data are very, very close individual animals, it really means that we have more to the line. (Editorial Note: it is rare to see such a high hairy shore crab. value of r2 on ecological plots!) That means that the number of shore crabs is a very accurate predictor This is an intriguing question that Crab Team doesn’t of the total number of organisms of all species that have an answer to—at the moment. After all, it’s only were trapped at the site. Note that the line doesn’t our first year. Here are some possibilities:

10 • Conditions that shore crabs are very good at When Do Crabs Celebrate Valentine’s Day? surviving, and where they do best, are not suitable And Other Observations on Behavior for many other species. • Shore crabs decrease the diversity of other species In addition to learning about ecological communities in places where they live, potentially by out- as a whole, we can learn about individual species from competing for resources, or even eating other trapping data. For instance, volunteers often report species directly. how many gravid (egg-bearing) females they find. We • Or, it could be related to sampling technique: at can use this opportunistically collected information to sites with many hairy shore crab, they fill up a trap identify peak reproductive times. Because we have the quickly. A trap of agitated pinchers might be less most data for hairy shore crab, our conclusions are appealing for some of the shy species to enter, so strongest for that species. Figure 7 is the total number those species might be present in the habitat, but of gravid females collected at all sites for each month not observed in the traps. duringreport 2016. Reproduction measuredof this2016 way shows findings two peaks, one in May and one in July/August. This is This is an excellent demonstration of how supported by previous research, which has found that observational studies like Crab Team can provide each female hairy shore crab can bear two broods of hypotheses about how the world works. These eggs in a single summer. The timing of those peaks ideas are potential starting points for future might change from year to year depending on study. temperature.

We can also learn about the crabs’ behavior by assessing the ratio of male to female crabs that enter traps. Many volunteers have noticed that the number of male hairy shore crab captured in traps is often, but not always, much greater than the number of females. Number of females with eggs

PHOTO CREDIT: JEFF ADAMS April May June July August Sept

A female hairy shore crab bearing eggs under her Month abdominal flap. Figure 7. Total number of female hairy shore crab (Hemi- grapsus oregonensis) captured in traps bearing eggs by month during 2016.

11 The predominance of males does not hold true for all our conclusions for hairy shore crab are stronger than species, however. Figure 8 is a scale of the seven most for hairy helmet crab, of which only four individuals common crab species in trapping surveys, arrayed were found. The gradient is scaled logarithmically along a gradient based on the sex ratio averaged across because the value for each species is a ratio. The dot- the entire 2016 trapping season. Note that the circles ted line at 1 indicates an equal number of males and representing each species are different sizes—they females. A sex ratio of five means that there are five have been scaled to reflect how many of that species times more males than females, but a sex ratio of 0.2 were captured total. Thus, as with egg-bearing females, means that there is one male for every five females—or five times as many females as males.

When we think about a species or population as a whole, we typically expect that the sex ratio should be closer to 1:1, so why would most of our crabs deviate from that ratio? Though for some organisms, there are behavioral, ecological, or biological factors that might cause an imbalanced sex ratio in the population, we suspect that the sex bias we observe is likely due to the effect of sampling and might occur for two reasons:

1) there are more crabs of one sex in the habitats we sample and/or 2) there are the same number of males as females in the habitat, but more of one sex enter traps.

If, for instance, female Dungeness crab disproportion- ately prefer the protected pocket estuaries where we sample, our result of a female-biased sex ratio reflects that habitat choice, rather than an assessment of the entire Dungeness crab population in the Salish Sea. For Dungeness crab, this seems most likely, as the females, being smaller, are often found in more protected habitats than the males.

A male-biased sex ratio might instead reflect behavior. The thought is that more males enter traps because they engage in greater risk-taking behavior in seeking food, because large size enables greater reproductive success. Entering a trap that is already full of pinchy claws is a risky proposition for a small crab. There is some evidence that, for hairy shore crab, males do take more risks than females. Figure 8. Sex ratio (male:female) of all crab species captured in traps during 2016. Size of circle indicates total number of One way we could test this question is by looking at individuals for that species/taxon captured. the sex ratio of crab molts (which is an observation we don’t currently collect); if it is closer to 1:1 averaged

12 over the season, then we could rule out the first season. Even though purple shore crabs are overall explanation. However, this method could also be much less numerous in traps than hairy shore crabs, biased if one sex grows faster than the other, comparing the change over time can still show similar producing more molts per individual. A second way trends if changes in season are affecting the species to test this is to use a type of trap that doesn’t require similarly. In this case, male hairy and purple shore crabs to make a decision to enter, such as a pitfall crabs appear in traps at similar relative abundances for trap. A pitfall trap is a bucket buried so the top is most of the season, with the exception of June. Females level with the sediment surface—crabs fal in as they of the two shore crabs species, however, show very walk across the mud. different patterns. Female hairy shore crabs increase fairly consistently over the summer, but female purple Sex ratio can also change over the course of the shore crabs show a “hump-shaped” pattern: low in April season, and that change can be different for different and September, but consistent in the middle of the species—even for similar species. Comparing the two season.report Why do females of theseof two species2016 show a findings species of native shore crab (Figure 9), we see that markedly different pattern? This remains an intriguing not only is the overall average sex ratio different, but question for future study. the trend over time is nearly opposite. Purple shore crab has a pronounced dip in June, then increases to a peak in September, while hairy shore crab decreases slightly, but steadily, over the course of the summer. 1.2 400 350 1 A lower sex ratio can occur either because fewer 300 males, or more females, are entering traps. In order 0.8 250 to figure out why these species differ, we can take a 0.6 200 look at each sex separately. Figure 10 shows trend in 150 abundance for both species over the course of the 0.4 100 0.2 50 Hairy shore crabs per site Hairy shore Purple shore crabs per site Purple shore 0 0 April May June July August Sept

1.2 80 1.4 70

1.2 60

1 50 0.8 40 0.6 30 0.4 20 0.2 10 Hairy shore crabs per site Hairy shore Purple shore crabs per site Purple shore 0 0 April May June July August Sept

Figure 9. Sex ratio (male:female) of hairy (Hemigrapsus Figure 10. Total number of male (top panel) and female oregonensis) and purple (H. nudus) shore crabs trapped by (bottom panel) hairy (Hemigrapsus oregonensis, right axis) and month. purple (H. nudus, left axis) shore crab captured by month.

13 3. Molt Surveys

nother way to learn about the Table 4. Total Molts Collected by Species. Total number of communities that live in the habitats we each taxon collected in molt surveys across all sites and Asample is by looking at their molts. Volunteers months during the 2016 monitoring season conduct standardized molt searches each month. By looking at molts we can find evidence of species that Molt Species Common Name # Found live in the area, but might not come to traps. We can Hemigrapsus oregonensis Hairy shore crab 12,095 also assess seasonality of growth for various species. Hemigrapsus nudus Purple shore crab 739 Cancer (Metacarcinus) magister Dungeness crab 128 During 2016, a total of 12 taxa of crustacean was Cancer productus Red rock crab 76 found in the molt surveys (Table 4). That’s close, Cancer (Metacarcinus) gracilis Graceful crab 49 indeed only one greater than, the number of Multiple in Amphipods 20 crustacean species that were found in traps, but Telmessus cheiragonus Helmet crab 18 the species were not the same. Some species were Multiple in Majidae Spider crabs 14 found only as molts, including pea crabs, burrowing Multiple in Thalassinidea Burrowing shrimp 6 shrimp and amphipods. We know that burrowing Pagurus spp. Hermit crabs 2 shrimp are common in and around pocket estuaries, Lophopanopeus bellus Black clawed crab 2 but because they are either filter or deposit feeders, Multiple in Pinnotheridae Pea crabs 1 we don’t expect them to come to our mackerel bait. Total 13,150 The only crab that was captured live that did not also appear as a molt was the European green crab. Funnily enough, in Crab Team’s rapid assessment trapping in Westcott Bay following the capture of the single European green crab, we did find a green Table 5. Commonness of Molts Collected. Number of sites crab molt, albeit not in a location we expected to at which each crustacean taxon was found in mmolt sur- find molts. veys during the 2016 monitoring season.

The order of crustacean species abundance is similar Molt Species Common Name # Sites in the trapping and molt data (Table 5), but large Where Found crabs, like Dungeness and rock crab, are found Hemigrapsus oregonensis Hairy shore crab 26 relatively more frequently as molts than they were Hemigrapsus nudus Purple shore crab 19 in traps, probably because their molts are easier to Cancer (Metacarcinus) magister Dungeness crab 18 |find and degrade more slowly than those of smaller Cancer (Metacarcinus) gracilis Graceful crab 11 species or individuals, for instance, hermit crabs. Cancer productus Red rock crab 10 Multiple in Majidae Spider Crabs 5 Telmessus cheiragonus Helmet crab 5 Multiple in Amphipoda Amphipods 2 Multiple in Thalassinidea Burrowing shrimp 2 Pagurus spp. Hermit crabs 2 Lophopanopeus bellus Black clawed crab 2 Multiple in Pinnotheridae Pea crabs 1

14 Learning How Communities Change Over Time And In Different Places, From Molts

We can learn about patterns of how many, and how many types of, there are by looking at data on molts. Figure 11 is a map of molt surveys, similar to the Figure 4 map, which is based on trapping data. The marker for each site is coded by size, where larger markers indicate a greater total number of molts found in hunts during 2016, and by color, where a darker marker indicates a greater number of molt taxa found during 2016.

Interestingly, sites that captured the most live crabs report of 2016 findings (Figure 4) didn’t always have the most molts. Deer Lagoon, the southern-most site on Whidbey Island, for instance, was second out of all our sites in c apturing the most live organisms. Yet, very few molts were ever found at this site. This is likely because site-related factors like wind and shoreline shape affect how many molts wash up on beaches.

Figure 11. Map of total abundance and species richness (number of taxa) of molts collected across 26 Crab Team monitoring sites during 2016. Larger circles mark sites with more total molts, and darker circles indicate that more taxa were found at that site.

PHOTO CREDIT: EMILY GRASON

Molts of the purple shore crab collected during the Crab Team molt survey.

15 Examining patterns of peaks in molts can tell us about periods of growth. Figure 12 shows the average number of molts of each species found per month at a typical site. While the numbers of each species vary (the darker lines indicate more molts of that species), peaks for a given species might indicate times of the year when that species is growing most rapidly. For hairy shore crab this appears to be May and September, while June was a clear peak for purple shore crab. When we find more molts overall, we can be more confident that a peak represents a change in growth rates for the species. However, species for which we found only a very few molts (hermit crabs, black-clawed crab and pea crabs) don’t really give us enough information to tell if observations represent a peak or just a rare sighting.

Figure 12. Total number of molts collected by survey month for each species found across 26 Crab Team monitoring sit1es during 2016. Species are ordered by most molts found (top) to fewest molts found (bottom).

PHOTO CREDIT: P. SEAN MCDONALD

Volunteers Caitlin Kenney and Gail Trotter tally the molts found during survey at Butterball Cove near Lacey.

16 4. Habitat Transect Surveys

f the three Crab Team protocols implemented we predict where green crab will show up and do well at each site—trapping, molt hunt and shore- based on how much vegetation, or eelgrass or trash, is Oline transect—only the first two actually present? Or, can we see changes in the vegetation, or involve looking for European green crab. The shoreline eelgrass, as a result of green crab population growth? transect protocol is designed to collect information By comparing sites with and without green crab, about the sampling site itself, how much of it is before and after arrival, we could start to disentangle anchored by vegetation, what the washed up debris the relationships with habitat factors that could help (wrack) can tell us about the surrounding habitat, etc. us prioritize other sites for protection. Collected over time, this information could help us understand how habitat influences green crab, and Figure 13 is a map of 2016 sampling sites, showing how vice versa. We know that green crab do well in pocket muchreport wrack each site had monthly, of on average,2016 and findings estuaries, but can we get more specific than that? Can what that wrack was made up of. The “wrackiest” site

Figure 13. Map of average wrack percent cover (size of circle) and composition (colors) by site.

17 was Lagoon Point on Whidbey Island. On average, each in about 16% more of the space in September month more than half of its shoreline was covered with than it did in April. Some of this increase is the some kind of washed up debris, mostly terrestrial vege- ssprouting of new seeds, filling in gaps, or the asex- tation. The three sites that were dominated by eelgrass ual growth of plants like saltgrass (Distichlis) that use in the wrack were all up north. rhizomes and runners to spread out and cover new territory. We might expect that, over the winter, storms will remove some of this new growth, but we’ll have to Learning How Sites Change Over Time wait until we analyze 2017 data to find out. And In Different Places, From Transect Live epifauna (living animals attached or sitting in place) Surveys and filamentous green algae are two categories we added in 2016. They are both rare, but present at some Collecting habitat information monthly enables sites. A stronger test of our hypotheses about seasonal us to explore seasonal patterns in shorelines. As trends in cover of live epifauna would be to zoom in on environmental factors such as nutrients wave intensity, sites that actually have some of that category. Percent temperature and the amount of time the intertidal zone is exposed at low tide change over the course of the year, they likely trigger changes in shoreline features. For instance, in late summer, we might expect to see more barnacles and mussels dying from heat or 60 long exposure to the air. We might also expect to see evidence of an increase in “primary production” 40 (growth by photosynthesizing organisms like eelgrass and seaweed) in the earliest months of sampling, when 20 nutrients are most available in the water. We might cover Percent even detect a shift from sand to mud as beaches settle 0 out after winter storms. April May June July August Sept Green crab could alter not only the habitat itself, Figure 14. Percent of habitat cover by category and month, but also the seasonal patterns in the habitat. For averaged across all sites. instance, in a typical year, we might see the percent cover of epifauna start to drop in July. But green crab looking for a meal could reduce populations of barnacles and mussels earlier in the year. If we 20 recorded observations on the habitat only once or twice a year, we would likely miss these changes. 15 Monthly surveys give us more time points to identify whether there is a trend or directional change in 10 features over the course of the seasons.

Percent cover Percent 5 Figure 14 shows the percent cover of each of the four substrate cover categories, averaged over all 0 April May June July August Sept the sites for each month. You’ll notice that nearly all of the space is either bare or covered with Figure 15. Percent cover of live epifauna by month at the vegetation, and that, on average, vegetation fills three sites where this category was detected in 2016.

18 cover of epifauna (averaged across the 10 quadrats) is during the winter, after the migratory brandt (geese) graphed for the three sites with the most live epifauna come through to graze on eelgrass and when storm (Figure15). The original hypothesis was that live waves break the long blades, we would probably see epifauna would decrease over the season due to much more eelgrass in the wrack. One positive note stress of daytime low tides. None of the sites show from these observations is that trash was very rare at this trend. Blakely Harbor and Penn Cove show a all of the sites. Is it possible the very slight uptick in possible, if weak, “U-shaped” trend, and Deer Lagoon September is the accumulated debris of many summer shows a marked increase in cover of live epifauna. vacations? This increase could be due either to population or individual growth—more mussels and barnacles or Sometimes, very small changes that happen over bigger mussels and barnacles. the course of several months aren’t apparent to our eyes alone. That is a major advantage of a large data What about the wrack? The amount of wrack observed set.report When these small changes of are aggregated 2016 over findings at the sites was highest in April, and that was mostly all of the sites, they become more obvious, and due to an abundance of washed up seaweed during conclusions about them more robust. As Crab Team that month (Figure 16). This does support our gathers more data about shoreline habitats, we’ll have prediction of a spring “bloom” of photosynthetic a better idea of which aspects show seasonal change growth. We don’t see the same trend in eelgrass in and how often we truly need to sample to capture the wrack, however, and that is probably because those changes. We can then use that knowledge to eelgrass is growing at that time, but staying rooted in assess whether we could simplify the transect protocol the deeper areas. If we were to conduct our surveys and still be confident that we weren’t losing the ability to detect changes.

15

10

5 Percent cover Percent

0 April May June July August Sept

Figure 16. Percent cover of wrack by category and month, averaged across all sites.

PHOTO CREDIT: SUSAN MADOR

Crab Team Intern, Natalie White, checks identification details with volunteer Charlie Seablom at Penn Cove on Whidbey Island.

19 Closing Thoughts

rab Team staff are immensely grateful for leading edge of a potential invasion. Because of the contributions of volunteers in helping volunteer participation, Washington’s Salish Sea Cbuild a monitoring program founded on has the best chance to avoid ecosystem impacts from robust and well-tested methodologies, ultimately this globally damaging invasive. In the role of sentinels, advancing the goals and impacts of citizen science. volunteers are also amassing a treasure trove of data Long-term data sets have been shown to be the on these relatively understudied habitats of the Salish most influential in effecting policy and management Sea. The value of this data set grows with each year change. Early detection monitoring by Crab Team added, and can be applied to other management volunteers and partners has undoubtedly enabled questions such as the health of restoration sites, us to do what has rarely been accomplished in and the ecological consequences of human invasion biology—detect and respond to the modifications to habitats.

PHOTO CREDIT: ALLEN PLEUS/WDFW

Crab Team Co-PI Sean McDonald and Nicole Burnett of the Padilla Bay NERR check traps set during the rapid assessment at Padilla Bay in 2016.

20 report of 2016 findings

Washington Sea Grant College of the Environment University of Washington 3716 Brooklyn Ave. N.E. Seattle, WA 98105-6716 206.543.6600 [email protected] • wsg.washington.edu wsg.washington.edu/crabteam/

21 Thank you for being part of the Crab Team 2016!

PHOTOS COURTESY OF CRAB TEAM STAFF AND VOLUNTEERS

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